The genealogies from Jesus College MS 20 are a medieval Welsh collection of genealogies preserved in a single manuscript, Oxford, Bodleian Library, Jesus College, MS 20, folios 33r–41r. It presents the lineages of a number of medieval Welsh rulers, particularly those of south Wales.[1] The manuscript was compiled in the late 14th century, but many genealogies are thought to be considerably older.[1] The latest pedigrees to have been included in the tract are those of Llywelyn ab Iorwerth (d. 1240) and Rhys Gryg (d. 1234).[1] It shares some material with the earlier Harleian genealogies.

Thornton, David E. Kings, chronologies, and genealogies: studies in the political history of early medieval Ireland and Wales. Occasional publications of the Oxford Unit for Prosopographical Research 10. Oxford: Linacre College, Unit for Prosopographical Research, 2003. ISBN1-900934-09-4